The use of certain transition metal compounds to polymerise 1-olefins, for example, ethylene or propylene, is well established in the prior art. The earliest catalysts for the catalysed polymerisation and copolymerisation of 1-olefins were the well-known Ziegler-Natta catalysts based on transition metal halide, e.g. titanium or vanadium chloride and an alkyl aluminium compound. More recently the use of certain metallocene catalysts (for example biscyclopentadienylzirconiumdichloride activated with alumoxane) has provided catalysts with potentially high activity. The use of metallocene based catalysts in the manufacture of EPM and EPDM elastomeric copolymers has been disclosed in, for Example, U.S. Pat. No. 6,545,088 (Dow Global Technologies Inc).